A luminaire is a system for producing, controlling, and/or distributing light for illumination. For example, a luminaire can include a system that outputs or distributes light into an environment, thereby allowing certain items in that environment to be visible. Luminaires are often referred to as “light fixtures”. Conventional luminaries typically use conventional optical systems, including, a total internal reflection (“TIR”) lens, a hybrid optical system which includes a refractor and a reflector combination system, and/or a single reflector, for obtaining a desired light distribution. However, at least two issues arise when using conventional optical systems. One is that the lens turns a yellowish color, thereby significantly reducing the efficiency of the light output. The yellowing issue is caused, in large part, because the lens is fabricated from a plastic material, such as a polymethylmethacrylate (“PMMA”) or acrylic, or a polycarbonate material, and turns slightly yellow in color when exposed to high temperatures and/or ultraviolet light over time. Yellowing of the lens significantly reduces the efficiency of the light output therethrough because less light is transmitted to an area that is intended to be illuminated.
The useful life of TIR and hybrid lenses can be significantly less than the life of the LED. Selecting a TIR lens material that equals or exceeds the life of the LED can be cost prohibiting for the light fixture market.
In addition, when using a single reflector to obtain the desired light distribution, a halo effect is often created on the area that is to be illuminated. FIG. 1 illustrates a halo effect in a light distribution pattern 100 formed when using a conventional luminaire 150 having a single reflector 170 in accordance with the prior art. Referring to FIG. 1, the conventional luminaire 150 includes the single reflector 170 having a first end 172 and a second end 174 and a light source 160 located adjacent to the first end 172. The first end 172 forms a first opening 173, while the second end 174 forms a second opening 175. The single reflector 170 has a parabolic or conical shape, with the first opening 173 being smaller than the second opening 175. The light source 160 is disposed within the first opening 173 and emits light through the second opening 175 towards an illuminated area 110. Thus, the first end 172 surrounds the light source 160. A portion of the light emitted from the light source 160 is directed towards the internal surface of the reflector 170, reflected, and re-directed to the illuminated area 110 through the second opening 175. This portion of the light creates a hot spot 102 (a small area of increased illumination) on the illuminated area 110. The remaining portion of the light is emitted directly from the light source 160 to the illuminated area 110 through the second opening 175. This remaining portion of the light creates an outer band 104, or outer ring, surrounding the hot spot 102 and at a lumen level below that of the hot spot 102, thereby creating an uneven light distribution on the illuminated area 110. The hot spot 102 and the outer band 104 collectively form the halo light distribution pattern 100.
One solution to correct the halo effect is to cover the second opening 175 with a diffuse lens (not shown). However, adding a diffuse lens increases the cost of the optical system and also reduces light output and light efficiency. Another solution to correct the halo effect is to increase the height of the reflector 170. However, doing so makes the single reflector 170 very tall, which would make using the single reflector 170 within existing light fixtures mechanically unfeasible. Additionally, increasing the height of the reflector 170 increases the amount of material costs.